Supplemental automotive vehicular heater system and method of providing same

ABSTRACT

A supplementary heating system particularly suitable for an automotive vehicle comprises a step down transformer coupled to the stator windings of the vehicle&#39;s alternator and a positive temperature coefficient (PTC) of resistivity heater electrically connected intermediate the stator windings and the transformer in parallel with the transformer. Due to the presence of the transformer the voltage regulator causes the alternator to operate at a higher than customary voltage to provide the conventional 14.4 volts for the vehicle&#39;s normal electrical loads with the high voltage used to energize the heater. The heater can be in the form of a so-called &#34;honeycomb&#34; having a plurality of parallely extending passages or cells disposed in the air stream going from the main heater into the passenger compartment and can be either a multiphase, single phase or direct current type. In one embodiment the transformer is switched into and out of electrical coupling with the alternator dependent on the energization of the heater, while in another embodiment the transformer is always electrically coupled to the alternator with the heater switched into and out of the circuit as desired.

This application is a continuation of application Ser. No. 069,665 filed07/06/87, now abandoned, which in turn is a continuation of applicationSer. No. 852,484, filed 04/16/86 which issued as U.S. Pat. No.4,678,982.

BACKGROUND OF THE INVENTION

The present invention relates generally to automotive vehiclar heatersand more specifically to supplemental heaters for such vehicles.

At the present time automotive vehicles conventionally are supplied withheating systems which utilize heat produced by the vehicle's engine. Thesystem includes a heater core comprising a conduit which mounts heatexchange fins. Water heated by the engine and transported through theconduit from the engine block gives up its heat through the fins to airwhich is caused to be passed among the fins. The heater core may, forexample, be configured to fit into a rectangular passage in the order ofsix by eight inches positioned in a duct which passes through the firewall separating the engine from the passenger compartment. A fanpositioned upstream of the heater core is adapted to force a flow of airthrough the heater core and into the passenger compartment. The fantypically is provided with a selection of speeds so that an operator canvary the volume of air being directed into the passenger compartment.The air passage typically includes a path which extends directly throughthe heater core as well as a parallel path which bypasses the heatercore with an adjustably positioned vent door (heater temperaturecontrol) provided to control the proportion of air directed through theheater.

In vehicles having relatively large engines, such as 6 or 8 cylinderengines, the heating systems are generally considered adequate, oncewarmed up, in providing sufficient heat to the passenger compartment.However, in vehicles having smaller engines, such as 4 cylinder engines,the engines are sometimes unable to produce enough heat tosatisfactorily warm up the passenger compartment on extremely cold days.This problem is actually becoming more acute as the engines are beingimproved to be more efficient and therefore give up less waste heat.

Another problem presented by present day automotive heating systems isthe time interval which exists between initial start up and when thermalequilibrium is eventually achieved. In some cars this may take ten orfifteen minutes or even longer depending on the particular ambienttemperature involved. Since the duration of an average trip is only inthe order of twenty minutes or so, much of the trip is conducted in anuncomfortable temperature condition for the operator and passengers.

Over the years various attempts have been made to deal with theseproblems however each has had limitations which have militated againstits usefulness and general acceptance.

For example, gasoline fired heaters are available but they are bulky,expensive to provide and maintain and they are slower than desirable.Use of exhaust gas heat has been suggested but problems with eliminatingany possibility of carbon monoxide gas leaking into the passengercompartment along with the relatively long warm up time required havemade this approach unsatisfactory.

Electric heaters have been proposed for supplemental defrost heaters andthe like but providing suitable energizing means has presented a problemwhich has not yet been satisfactorily solved. Typically an automobile isprovided with an alternator which has a field winding adapted to bemechanically rotated by the engine to produce electric current to runthe various electric loads of the vehicle. Since most of the electricloads of the car are sensitive to voltage variations a voltage regulatoris provided to maintain the voltage level, within a very narrow range,at 14.4 volts (DC), suitable for most of the electric loads. Thealternator is adapted to provide the voltage level despite beingsubjected to a wide variation of energization of the electric loads andvarying mechanical input, e.g. engine speeds ranging from idle toracing. A typical large automotive alternator, operated to provide 14.4volts, produces in the order of 1500 watts and since the electric loadsnormally consume 1000 or more watts, there is little power available toprovide desired supplemental heat.

However an alternator can be run at a higher voltage to increase itsoutput power. For example, it has been proposed that a deicing heater ina windshield be heated by energizing a resistive clear coating betweentwo layers of glass. Since this requires a relatively large amount ofpower, the proposal entails disconnecting the alternator from thebattery, then running the alternator at a higher voltage to providesufficient power for the windshield heater and to energize the remainingelectric loads in the car directly from the battery. In this system theheater can only be energized while the car is in the "PARK" position.Since the car cannot be operated while the heater is in operation thiswould be an unsuitable approach as a way to supplement the heater forthe passenger compartment, particularly since it can only address thewarm up interval and not the problems associated with continuousoperation of smaller, 4 cylinder engines.

Another proposal has involved the provision of dual alternators, oneoperated at 14.4 volts for the normal automotive loads and the second atan elevated voltage for a supplemental heater. This, however, is notonly costly initially, it is the type of component subject to wear andeventual replacement representing a significant cost item. In additionthis would be relatively bulky and heavy.

Yet another problem associated with alternator powered heaters involvesthe selection of a heater which would work satisfactorily with thecharacteristics of the alternator. That is, the heater must be operablewith certain widely varying variables. For example, if used as asupplemental heater to add heat to the air stream passing through themain heater core, the heater must be capable of operating with the fanoff as well as with the fan on at its maximum position (fullcirculation). A compromise in performance is usually required in orderto avoid overheating and burn out of the heater. That is, the heatermust be constructed so as to be able to generate heat without burningout with a minimum of heat dissipation when the fan is off as well aswhen the fan increases heat dissipation.

Voltage variations pose another problem for the selection of a heatingsystem. For example, when the engine slows down or idles, the alternatorvoltage tends to drop. With a conventional wire heater having anessentially fixed electrical resistance, a change in voltage has aneffect on heat produced which is dependent on the square of the voltagevariation so it becomes very difficult to maintain a desirable even heatoutput.

It is therefore an object of the invention to provide an improvement inthe performance of a heating system of an automotive vehicle. Anotherobject is the provision of a method and apparatus to supplement the mainheating system of an automotive vehicle so that the waiting time betweeninitial energization and a thermal equilibrium for a selectedtemperature in the passenger compartment is significantly reduced.Another object is the provision of a method and apparatus to supplementthe main heating system of an automotive vehicle which otherwise hasdifficulty in achieving a satisfactory comfort level in cold ambientconditions. Yet another object is the provision of a supplementalheating system which is relatively inexpensive yet extremely reliable,one which can provide even heat output even with changing voltageconditions and one which minimizes changes in currently employedautomotive components and does not interfere with the normal operationof the vehicle.

SUMMARY OF THE INVENTION

Briefly, in accordance with the invention, a transformer is coupled tothe stator windings of the alternator of the vehicle so that the voltageregulator forces the alternator to operate at an elevated voltage torealize greater output power from the alternator. The high voltage poweris tapped off intermediate the stator windings and the transformer andis used to energize an electric heater to supplement the main heater ofthe vehicle.

According to a feature of the invention in a first embodiment apolyphase, typically a three phase supplemental heater having a positivetemperature coefficient of resistivity is coupled directly to the highvoltage while in a second embodiment a direct current supplementalheater having a positive temperature coefficient of resistivity iscoupled to the high voltage through a rectifier.

According to another feature of the invention the supplemental heater isin the form of a so-called honeycomb configuration having a plurality ofpassages or cells through which air circulated by the heater fan iscaused to pass.

According to yet another feature a double throw relay is provided foreach phase of the transformer having a common terminal connected to theinput of the rectifier which provides power to the automotive loads.Each relay has one terminal connected to a point intermediate arespective alternator stator winding and a single throw switch whoseother side is connected to the three phase heater and input of thetransformer. The other terminal is connected to the output of thetransformer. Thus when the heater is not energized, the alternator isoperated in a conventional manner and when the heater is energized, therelays are switched so that the transformer is in the circuit forcingthe alternator to operate at an elevated voltage level in order tomaintain the desired 14.4 volt level for the other automotive electricloads.

According to another embodiment of the invention rather than employingrelays to switch the main load current of the automobile, single throwswitches or relays are placed in at least two lines leading from thestator winding to the three phase heater so that the alternator isalways operated at an elevated voltage whether or not the heater isenergized.

According to another feature of the invention the three phase heatercomprises a plurality of honeycomb elements arranged in a frame adaptedto be placed in an air passage or duct so that the air will pass throughopen cells formed in the honeycomb elements. The elements areelectrically connected in a delta configuration but physically disposedin the frame to provide a generally even electrical load among thephases despite fluid flow variations across the cross section of theduct.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features, advantages and details of the supplementalheater system and method of providing same provided by this inventionappear in the following detailed description of preferred embodiments ofthe invention, the detailed description referring to the drawings inwhich:

FIG. 1 is a schematic diagram showing a supplemental heater system madein accordance with the invention;

FIG. 1a is a broken away schematic diagram showing a modification of theFIG. 1 system;

FIG. 2 is a schematic plan view of a heater configuration particularlyuseful with the FIG. 1 embodiment;

FIG 2a is an enlarged cross sectional view taken on lines 2a--2a of FIG.2;

FIG. 3 is a schematic flow diagram showing the main components of theheater system;

FIG. 4 is a graph showing voltage versus current for several alternatorspeeds of a typical automotive alternator;

FIG. 5 is a graph showing power versus current for the same alternatorspeeds and the same alternator as used for FIG. 4; and

FIG. 6 is a schematic diagram similar to FIG. 1 of an alternateembodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, numeral 10 refers generally to the heatingsystem made in accordance with a first preferred embodiment of thepresent invention. A conventional automotive alternator 12 such as aDelco-Remy CS 144, 120 ampere alternator has three delta connectedstator windings 14, 16, 18 with output line 20 connected betweenwindings 14, 16, output line 22 connected between windings 14 and 18 andoutput line 24 connected between windings 16 and 18. A field winding 26is adapted to be rotated by the vehicle's engine adjacent to the statorwindings in a known manner so that direct current caused to flow throughfield winding 26 upon rotation thereof will generate current in thestator windings. A transformer 28 comprising wye connected windings 30,32, 34 is arranged so that winding 30 is connected to output line 20through a single throw switch 36a, winding 32 is connected to outputline 22 through a single throw switch 36b and winding 34 is connected tooutput line 24 through a single throw switch 36c. Switches 36a, b and care ganged together so that they will all be in the opened or closedposition at the same time and are also tied to the operation of doublethrow switches 36d, e and f. Switch 36d has one terminal connected towinding 30 through line 38 and its other terminal connected toalternator output line 22 through line 40. Switch 36e has one terminalconnected to winding 32 through line 42 and its other terminal toalternator output line 20 through line 44. Switch 36f has one terminalconnected to winding 34 through line 46 and its other terminal connectedto alternator output line 24 through line 48. The common terminals ofswitches 36d, e and f are all coupled to a conventional rectifier 50which has an output line 52 connected to the various vehicle electricloads 54 (lights, radio, instruments, etc.) in parallel with battery 56.Switches 36d, e and f are ganged together so that they all assume likepositions as will be explained further below.

A three phase heater assembly 58 comprising heater sections 60, 62 and64 are connected to the alternator output lines intermediate switches36a, b and c and transformer 28. Heating sections 60, 62 and 64 areshown to be connected in a delta configuration with section 60 connectedbetween output lines 20 and 22, section 62 between output lines 20 and24 and section 64 between output lines 22 and 24. Preferably heaterassembly 58 is comprised of self-regulating electrically resistivematerial having a positive temperature coefficient (PTC) and is formedas a body having a honeycomb configuration in which a plurality ofparallely extending passages or cells extend between opposite faces ofthe body. With particular reference to FIGS. 2 and 2a heater assembly 58comprises a plurality of identical bodies 60, 62 and 64 of ceramicmaterial or the like of positive temperature coefficient of resistivityhaving a large number of passages 60a, 62a and 64a respectively,extending through the body in side-by-side parallel relation to eachother between opposite faces or ends of the body. The passage walls (see62b in FIG. 2a) define thin webs of the resistance material betweenadjacent passages in the body and the walls of the passages are ofuniform thickness from end to end.

Preferably the bodies comprise a ceramic material such as lanthanumdoped barium titanate or the like in which the material is adapted todisplay a sharp, anomolous increase in resistivity when the body isheated to a particular temperature and may be of the type described inU.S. Pat. No. 4,264,888.

A conductive coating is disposed on the walls of the passages with thecoating interconnected so that alternate cells are connected to twoseparate electrical conductors, as shown schematically in FIG. 2a,conductors 1a and 2a.

Bodies 60, 62 and 64 are physically mounted in a suitable frame shownschematically in FIG. 2 by numeral 66, which is adapted to be placedacross an air stream in a duct carrying air from the main heater fan tothe passenger compartment as indicated in FIG. 3.

Frame 66 is shown to be an electrical conductor however it will beunderstood that in practice the frame could be constructed ofelectrically insulative material suitable for physically mounting thebodies and which in turn mounts a suitable electrical conductor.

As seen in FIG. 2, from left to right, a first group of bodies 62 aredisposed in electrically parallel relation between electrical connectors1b and 2b. A second group of bodies 64 are disposed in electricallyparallel relation between electrical connectors 2b and 3b and a thirdgroup of bodies 60 are disposed in electrically parallel relationbetween electrical connectors 3b and 1b. These three groups are thenduplicated to provide heater bodies across the entire cross sectionalsurface of the frame. Connector 1b is electrically connected toconductor 1 through frame 66 and connectors 2b and 3b are connected toconductors 2 and 3 respectively. Thus the bodies are arranged so thattwo spaced groups of bodies 62 will conduct current through webs 62bfrom alternator winding 16, spaced groups of bodies 64 will conductcurrent through its webs from alternator winding 18 and spaced groups ofbodies 60 will conduct current through its webs from alternator winding14. The groups of each body are preferably spaced from one another inorder to provide a balanced load in the event that air flow variesacross the cross sectional area of the duct. It will be understood thatif desired, a greater number of spaced groups of bodies for each phasecould be provided to increase the balance among the phases. Further, thenumber of bodies within the groups can be varied as long as it is variedin like manner in all the groups.

Turning back to FIG. 1, a controller 68 is used to control energizationof heater assembly 58. When an input is entered into the controller asby an operator turning on a switch to energize the heater, an output istransmitted to an electromagnetically operated relay 70 in series withfield winding 26 to open the relay contacts deenergizing the fieldwinding to interrupt generation of electricity by the alternator.Immediately following deenergization of field winding 26 the controllertransmits a signal to relay 36 to close switches 36a, 36b and 36c andmoving switches 36d, 36e and 36 f to the position in which they connectrectifier 50 to transformer 28. Once this occurs relay contacts 70 arereclosed to energize the field winding. This sequence can occur in afraction of a second. Due to the addition of the transformer to thecircuit the voltage regulator 72 now causes the alternator to operate ata higher voltage in order to maintain the selected 14.4 volts for carloads 54. This higher voltage results in greater power availability, aswill be discussed in greater detail below and is used to power theheater assembly 58. When it is no longer desired to have heater assembly58 energized inputting the controller 68 with an off signal eithermanually or automatically will again cause relay 70 to open its contactsthereby deenergizing field winding 26 at which point relay 36 isactuated to open switches 36a, 36b and 36c and move switches 36d, 3e and36f to disconnect the rectifier from the transformer and connect itdirectly to the alternator via lines 40, 44, 48. Relay contacts 70 arethen closed to reenergize the field winding which will then cause thealternator to operate at its lower voltage range to provide the selected14.4 volts. Although it is not essential to deenergize the field windingbefore actuation of relay 36, it is preferred to do so since relay 36carries the main electrical current for the various vehicle loads andswitching the relays at a time when they are not carrying currentenhances their longevity.

If it is desired to provide various protective devices for the componentparts of the system, they can provide an input to controller 68 toprevent energization of the heating assembly in the event of somemalfunction. For example, over temperature protection for thetransformer can be provided by placing a protector in each transformerwinding and connecting the protectors in series so that anovertemperature condition in any winding will deenergize the heatingassembly through control 68.

Operation of the heater assembly in this way enables one to use anessentially conventional alternator to provide the extra power neededfor a supplemental electric heater. With reference to FIG. 4 severalcurves are shown derived empirically from a 120 amp alternator showingvoltage versus current for different alternator speeds. FIG. 5 showingpower versus current indicates the power available at the alternatorspeeds used in FIG. 4. It will be seen that in the vacinity of 90 ampsat most alternator speeds maximum power is obtained from the alternator.Looking at FIG. 5, for example, at 4500 rpm over 3000 watts of power isavailable if the alternator is operated at approximately 36 volts DC(FIG. 4) but if one were to operate that same alternatorat 14.4 DC voltsas is done at the present time in conventional automotive vehicles onlyapproximately 1500 watts is obtained. In other words, conventionally thealternator is normally being operated at a value which is not optimum interms of outputting its maximum amount of power. Apparently thissituation has developed as a way of dealing with the constantly changingconditions in the operation of a vehicle in order to provide the powerneeded for varying current demands.

According to a system made in accordance with FIG. 1, transformer 28 waschosen to have a ratio of approximately 2 1/2 to 1 to operate thealternator at the equivalent DC voltage of approximately 36 volts (14.4volts×2.5) and was mounted externally of the alternator to facilitateair cooling of the transformer to allow the use of a smallertransformer. The transformer was connected to the stator windingsthrough separate taps installed in the windings. It will be understood,however, that the transformer could be installed in the same housing asthe alternator if so desired.

The above described system can be used to supplement a four cylindertype vehicle which has marginal heating system performance to bring itup to an improved performance level. It can also be used in larger sixor eight cylinder vehicles in order to greatly diminish the time periodrequired to bring the passenger compartment to a comfortable temperaturelevel. By using approximately two thousand watts from the alternator,air can be heated approximately 40° F. almost instantaneously, i.e.within a matter of five seconds using heater bodies 60, 62, 64. Thisheat, added to the air stream passing through the main heatersignificantly decreases the time needed to reach a comfortabletemperature level.

Although conventional fixed resistance heaters can be used in carryingout the invention, PTC heaters work particularly well for severalreasons.

One reason relates to voltage variations caused by, among other things,use of the transformer. That is, as more or less current is drawnthrough the transformer, the transformer ratio changes slightly, perhapsin the order of plus or minus ten percent in the instant case. With afixed resistance heater, since power is dependent upon the square ofcurrent, a swing of twenty percent in voltage would cause an evengreater change in output power thereby causing noticeably uneven heatoutput, however a similar change in voltage applied to a PTC heater hasonly a negligible effect on power, in the order of one percent or less.There are also low voltage conditions which can occur when all theelectrical loads in the vehicle are activated and the vehicle's engineis idling. For example, voltage may decrease to 12.5 volts which wouldresult in an equivalent DC voltage of 31 volts available for the heaterusing a 2 1/2 to 1 transformer. Heat output with a fixed resistanceheater would thereby be much more uneven compared to the heat output ofa PTC heater.

Other factors involve air flow effected by blower speed and blend door(temperature) position. Use of a fixed resistance heater wouldnecessitate a compromise in performance since measures would have to betaken to avoid heater burn out. That is, the heater would have to becapable of operation at low as well as high fan speeds and with all or aportion of the air flow being bypassed by the position of the blend orvent door. A PTC heater on the other hand automatically adjusts itsresistance as its heat dissipation changes without any danger ofoverheating.

Yet another advantage in using a PTC heater is the ability to controlthe inrush current upon initial energization. By formulating thematerial to have a selected low base resistivity at normal ambienttemperature and a selected web thickness, the inrush current can besignificantly increased to ensure rapid heat up of the PTC bodies. For aheater assembly designed to consume approximately two thousand watts ata steady state condition a heating assembly made in accordance with theinvention referred to above was adapted to draw an inrush currentapproximately twice the steady state value. Thus when the heater isenergized, it takes the entire alternator output for five seconds or sowhile the PTC bodies heat up (perhaps half the time it would otherwisetake) and during which time the remaining vehicle loads are energized bythe battery. When the heater assembly is energized, the voltage onoutput lines 20, 22, 24 drops to approximately 24 volts (equivalent DC)which is below the threshold voltage required for current to flowthrough the transformer since the battery provides approximately 12 1/2volts on the other side of the transformer. Once the PTC bodies areheated the power requirements automatically throttle back to the twothousand or so watts leaving sufficient power produced by the alternatorfor the vehicle loads and normal recharging of the battery. Thus thesystem is such that rapid generation of supplemental or incremental heatto a heating system is optimized.

FIG. 1a shows a modification of the FIG. 1 system in which the output ofalternator 12 is rectified through a conventional rectifier 74 similarto rectifier 50 to provide direct current for a heater 76 which couldtake the form of one or more PTC honeycomb bodies or, if desired, couldbe some other PTC heater for defogging the side view mirror or the likeor could even be a straight resistance heater requiring high power if itis not adversely affected by voltage variations and the like. An examplecould be a heater in the vehicle's rear window or possibly a frontwindshield deicing heater.

FIG. 6 shows an embodiment similar to FIG. 1 except that transformer 28is always electrically coupled to alternator 12 with heating assembly 58adapted to be energized and deenergized through a relay 80. Relay 80includes movable switch contacts in at least two of the phase conductorssuch as 80a in line 2 and 80b in line 3. The transformer windings 30,32, 34 are permanently connected to rectifier 50 through lines 38, 42,46 respectively. Thus alternator 12 operates continuously at a highervoltage with relay 80 switching heating assembly in and out of circuitrelation with the stator windings as desired. In other respects theoperation of the system is the same as that of FIG. 1 described above.This embodiment is particularly advantageous in that the main current ofthe vehicle is not switched and fewer switches are required foroperation. Since there is no main current switching, it may not benecessary to deenergize the alternator field before switching therelays, to thereby simplify or even eliminate controller 68.

It should be understood that although preferred embodiments of the noveland improved heating system have been described in detail forillustrating the invention, this invention includes all modificationsand equivalents of the described embodiments falling within the scope ofthe appended claims.

What is claimed is:
 1. An automotive vehicle having an engine and aplurality of electrical loads, an alternator having a field windingdriven by the engine to provide electrical power for such loads, avoltage regulator for controlling the field winding energization, thealternator having a stator with three windings, the windings coupledtogether to provide a three phase output on three output lines, theoutput lines connected to a rectifier which in turn is connected to acircuit including the plurality of electrical loads, the voltageregulator controlling the level of energization of the alternator fieldin order to provide a selected voltage level in the circuitcharacterized in that transformer means are coupled between the threewindings and the rectifier and an electrical resistor heater is coupledto the output lines intermediate the windings and the transformer means.2. An automotive vehicle according to claim 1 further characterized inthat means are provided to control the state of energization of theelectrical resistor heater including in each output line a first doublethrow switch having a common terminal and first and second terminals,the common terminal connected to the rectifier, the first terminalconnected to the stator winding, the second terminal connected to thetransformer, and a second single throw switch in the output line betweenthe stator and the transformer to connect and disconnect the stator andthe transformer, the first and second switches interconnected so thatwhen the second switch connects the stator and the transformer the firstswitch is connected to the said second terminal and when the secondswitch disconnects the stator and the the transformer the first switchis connected to the said first terminal.
 3. An automotive vehicleaccording to claim 2 further characterized in that means are provided todeenergize the field winding immediately prior to and to maintaindeenergization of the field winding and during the switching of thefirst and second switches.
 4. An automotive vehicle according to claim 1further characterized in that the electrical resistor heater is a directcurrent heater and a rectifier means is connected between the outputlines and the heater.
 5. An automotive vehicle according to claim 4further characterized in that the electrical resistor heater is composedof material having a positive temperature coefficient of resistivity. 6.An automotive vehicle according to claim 1 further characterized in thatthe electrical resistor heater is a three phase heater.
 7. An automotivevehicle according to claim 6 further characterized in that theelectrical resistor heater is composed of material having a positivetemperature coefficient of resistivity.
 8. An automotive vehicleaccording to claim 6 further characterized in that the electricalresistor heater is composed of material of positive temperaturecoefficient of resistivity having a plurality of passages arranged inthree groups extending therethrough in spaced side by side relation toeach other in a selected pattern defining thin webs of the heater whichare of substantially uniform thickness between adjacent passages fromend to end of the heater, electrically conductive means on inner wallsof the passages and electrically conducting interconnecting meanselectrically connecting the conductive means of the passages in eachgroup together, whereby, when the groups are connected in a circuit torespective output lines three phase current is directed through thinwebs of resistor material between the conductive means of one group andthe conductive means of another group in adjacent body passages.
 9. Anautomotive vehicle according to claim 6 further characterized in thatthe heater comprises a frame disposed in an air duct, the frame mountingthree sets of bodies, each body composed of materials of positivetemperature coefficient of resistivity having a plurality of passagesextending through the body in spaced side by side relation to each otherin a selected pattern defining thin webs of the body which are ofsubstantially uniform thickness between adjacent passages from end toend of the body, electrically conductive means on inner walls of thebody passages andelectrically conducting interconnecting means disposedon the body electrically connecting selected conductive means together,the electrically conductive means on each set of bodies being connectedto a respective output line whereby three phase current is directedthrough thin webs of resistor body material.
 10. An automotive vehicleaccording to claim 6 further characterized in that the electricalresistor heater is composed of three sets of bodies, each body iscomposed of material of positive temperature coefficient of resistivityhaving a plurality of passages extending through the body in spaced sideby side relation to each other, electrically conductive means disposedon spaced surfaces of the body, the electrically conducting means oneach set of bodies being connected to a respective output line whereby asingle phase of the three phase current is directed through eachrespective set of bodies.
 11. A method of providing supplemental heat tothe main heating system of an automotive vehicle having an alternatorwith stator windings and a field winding energized under the control ofa voltage regulator to provide a selected voltage level for thevehicle's normal electrical loads comprising the steps of interposing atransformer winding between each stator winding and the said normalelectrical loads so that the alternator is caused to operate at a highervoltage by the voltage regulator in order to provide the said selectedvoltage levels for the said normal electrical loads and electricallyconnecting a resistive heater to the stator windings intermediate thestator windings and the transformer windings so that the heater will beenergized by voltage levels higher than the said selected level.
 12. Amethod according to claim 11 further including the step of placing theheater in heat transfer relation with air in an air duct which isarranged to carry air from the main heater of the vehicle into thepassenger compartment.
 13. An engine and a plurality of electricalloads, an alternator having a field winding driving by the engine toprovide electrical power for such loads, a voltage regulator forcontrolling the field winding energization, the alternator having astator with at least one winding, the stator winding adapted to providean output on an output line, the output line coupled to a circuitincluding the plurality of electrical loads, the voltage regulatorcontrolling the level of energization of the alternator field in orderto provide a selected voltage level in the circuit characterized in thattransformer means are coupled between the stator winding and the saidcircuit and an electrical resistor heater is coupled to the output lineintermediate the winding and the transformer means.
 14. An automotivevehicle according to claim 13 further characterized in that theelectrical resistor heater is composed of material having a positivetemperature coefficient of resistivity.